蘋果冷庫氣體環(huán)境影響因素及通風(fēng)調(diào)控策略研究
發(fā)布時間：2019-01-24 11:50
【摘要】：冷藏庫內(nèi)氣體組分及其濃度分布是影響果蔬貯藏質(zhì)量的重要因素,而通風(fēng)換氣是保證庫內(nèi)合理氣體環(huán)境的關(guān)鍵過程。果蔬貯藏過程中CO2和C2H4濃度過高會影響果蔬食用及商用價值。而實際通風(fēng)換氣過程存在人為操作的隨意性,不僅使通風(fēng)效果不盡理想還會造成不必要的能源消耗。因此,研究蘋果冷庫CO2和C2H4氣體分布情況及通風(fēng)換氣過程影響因素,對探究庫內(nèi)氣體環(huán)境形成機(jī)理及制定通風(fēng)策略具有重要的學(xué)術(shù)意義和工程應(yīng)用價值,也為其他類型果蔬貯藏庫的通風(fēng)換氣機(jī)制研究提供一定的參考價值。本文用氣相色譜法對蘋果乙烯釋放規(guī)律進(jìn)行了實驗研究;并針對實際冷藏間建立了庫內(nèi)氣體流動與傳熱傳質(zhì)的三維數(shù)學(xué)物理模型,通過數(shù)值模擬研究,獲得了冷藏庫氣體組分分布規(guī)律及不同冷風(fēng)機(jī)運行模式、排風(fēng)速度和排風(fēng)口設(shè)置對庫內(nèi)CO2和C2H4分布的影響,主要研究工作如下:(1)采用氣相色譜儀對冷藏條件下蘋果乙烯釋放進(jìn)規(guī)律行研究,得到蘋果貯藏初期乙烯釋放量較大,且乙烯釋放量會隨著貯藏濃度的增加而變大,因此蘋果在貯藏過程中應(yīng)及時關(guān)注庫內(nèi)乙烯含量,合理進(jìn)行通風(fēng)換氣。(2)采用編寫UDF程序的方法解決了冷庫內(nèi)的兩個復(fù)雜問題,即貨物區(qū)蘋果的呼吸強(qiáng)度及冷風(fēng)機(jī)送風(fēng)口CO2和C2H4質(zhì)量分?jǐn)?shù)隨貯藏環(huán)境中氣體濃度的變化而改變這;并通過實驗測量驗證了該方法的可靠性。(3)運用CFD軟件模擬研究了冷藏環(huán)境CO2和C2H4的分布規(guī)律。模擬結(jié)果表明:蘋果貯藏24 h后庫內(nèi)貨物區(qū)和氣體區(qū)CO2和C2H4濃度分布比較均勻,但濃度偏高,貨物區(qū)二氧化碳濃度為2.8%,乙烯濃度超過15 ppm,均已超過蘋果冷藏貯存要求。(4)從通風(fēng)換氣過程影響因素出發(fā),對通風(fēng)換氣過程中冷風(fēng)機(jī)的啟停、排風(fēng)速度和排風(fēng)口設(shè)置對庫內(nèi)氣體濃度分布的影響進(jìn)行了研究。研究結(jié)果表明:開啟冷風(fēng)機(jī)時庫內(nèi)氣流擾動增強(qiáng),通風(fēng)換氣性能變差,因此提出通風(fēng)時應(yīng)關(guān)閉冷風(fēng)機(jī);隨著排風(fēng)速度的增加庫內(nèi)氣流的傳質(zhì)作用得到增強(qiáng),貯藏環(huán)境得到改善,換氣效果更好,并且存在一個最小排風(fēng)速度,使庫內(nèi)有害氣體濃度在規(guī)定的時間內(nèi)降低到貯藏要求,本文所研究冷庫,最小排風(fēng)速度可選8 m/s;雙排風(fēng)扇形式可以改善庫內(nèi)氣流組織,與傳統(tǒng)單排風(fēng)扇形式相比可以更加快速高效地降低貨物區(qū)有害氣體濃度。
[Abstract]:The distribution of gas components and their concentration in cold storage is an important factor affecting the storage quality of fruits and vegetables, and ventilation and air exchange is the key process to ensure a reasonable gas environment in the reservoir. The high concentration of CO2 and C2H4 will affect the edible and commercial value of fruits and vegetables. However, the actual ventilation and air exchange process has the randomness of artificial operation, which not only makes the ventilation effect not ideal, but also causes unnecessary energy consumption. Therefore, it is of great academic significance and engineering application value to study the distribution of CO2 and C2H4 gas and the influencing factors of ventilation and ventilation process in apple cold storage, which is of great academic significance and engineering application value in exploring the formation mechanism of gas environment and formulating ventilation strategy in the reservoir. It also provides some reference value for the study of ventilation and air exchange mechanism of other types of fruit and vegetable storage. In this paper, an experimental study on ethylene release from apple by gas chromatography was carried out. A three-dimensional mathematical and physical model of gas flow and heat and mass transfer in a cold storage room is established. Through numerical simulation, the distribution of gas components and the operation modes of different air coolers are obtained. The effects of exhaust air velocity and outlet setting on the distribution of CO2 and C2H4 in the storage were studied as follows: (1) the ethylene release from apple was studied by gas chromatograph under the condition of cold storage. And the amount of ethylene released will increase with the increase of storage concentration. Therefore, during storage, apple should pay attention to the content of ethylene in storage. (2) two complicated problems in the cold storage are solved by the method of writing UDF program. That is to say, the respiration intensity of apple and the mass fraction of CO2 and C2H4 in the air outlet of the air cooler changed with the change of the gas concentration in the storage environment. The reliability of the method is verified by experimental measurement. (3) the distribution of CO2 and C2H4 in refrigerated environment is simulated by CFD software. The simulation results showed that the concentration distribution of CO2 and C2H4 in storage area and gas area of apple was uniform after 24 h storage, but the concentration was on the high side. The concentration of carbon dioxide in cargo area was 2.8, and the concentration of ethylene was more than 15 ppm,. (4) based on the factors affecting the ventilation and ventilation process, the effects of the starting and stopping of the air cooler, the velocity of the exhaust air and the setting of the outlet on the distribution of the gas concentration in the storehouse were studied. The results show that the air disturbance in the storehouse becomes stronger and the ventilation performance becomes worse when the cold air machine is opened, so it is suggested that the air cooler should be closed when ventilating. With the increase of the exhaust velocity, the mass transfer of the air in the reservoir is enhanced, the storage environment is improved, the air exchange effect is better, and there is a minimum exhaust air velocity, which reduces the concentration of harmful gas in the reservoir to the storage requirement within the specified time. In the cold storage studied in this paper, the minimum exhaust velocity can be chosen as 8 m / s; The double exhaust fan can improve the airflow distribution in the reservoir. Compared with the traditional single exhaust fan, it can reduce the concentration of harmful gas in the cargo area more quickly and efficiently.
【學(xué)位授予單位】：西安建筑科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TU834
本文編號：2414450
[Abstract]:The distribution of gas components and their concentration in cold storage is an important factor affecting the storage quality of fruits and vegetables, and ventilation and air exchange is the key process to ensure a reasonable gas environment in the reservoir. The high concentration of CO2 and C2H4 will affect the edible and commercial value of fruits and vegetables. However, the actual ventilation and air exchange process has the randomness of artificial operation, which not only makes the ventilation effect not ideal, but also causes unnecessary energy consumption. Therefore, it is of great academic significance and engineering application value to study the distribution of CO2 and C2H4 gas and the influencing factors of ventilation and ventilation process in apple cold storage, which is of great academic significance and engineering application value in exploring the formation mechanism of gas environment and formulating ventilation strategy in the reservoir. It also provides some reference value for the study of ventilation and air exchange mechanism of other types of fruit and vegetable storage. In this paper, an experimental study on ethylene release from apple by gas chromatography was carried out. A three-dimensional mathematical and physical model of gas flow and heat and mass transfer in a cold storage room is established. Through numerical simulation, the distribution of gas components and the operation modes of different air coolers are obtained. The effects of exhaust air velocity and outlet setting on the distribution of CO2 and C2H4 in the storage were studied as follows: (1) the ethylene release from apple was studied by gas chromatograph under the condition of cold storage. And the amount of ethylene released will increase with the increase of storage concentration. Therefore, during storage, apple should pay attention to the content of ethylene in storage. (2) two complicated problems in the cold storage are solved by the method of writing UDF program. That is to say, the respiration intensity of apple and the mass fraction of CO2 and C2H4 in the air outlet of the air cooler changed with the change of the gas concentration in the storage environment. The reliability of the method is verified by experimental measurement. (3) the distribution of CO2 and C2H4 in refrigerated environment is simulated by CFD software. The simulation results showed that the concentration distribution of CO2 and C2H4 in storage area and gas area of apple was uniform after 24 h storage, but the concentration was on the high side. The concentration of carbon dioxide in cargo area was 2.8, and the concentration of ethylene was more than 15 ppm,. (4) based on the factors affecting the ventilation and ventilation process, the effects of the starting and stopping of the air cooler, the velocity of the exhaust air and the setting of the outlet on the distribution of the gas concentration in the storehouse were studied. The results show that the air disturbance in the storehouse becomes stronger and the ventilation performance becomes worse when the cold air machine is opened, so it is suggested that the air cooler should be closed when ventilating. With the increase of the exhaust velocity, the mass transfer of the air in the reservoir is enhanced, the storage environment is improved, the air exchange effect is better, and there is a minimum exhaust air velocity, which reduces the concentration of harmful gas in the reservoir to the storage requirement within the specified time. In the cold storage studied in this paper, the minimum exhaust velocity can be chosen as 8 m / s; The double exhaust fan can improve the airflow distribution in the reservoir. Compared with the traditional single exhaust fan, it can reduce the concentration of harmful gas in the cargo area more quickly and efficiently.
【學(xué)位授予單位】：西安建筑科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TU834
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